1. Field of the Invention
The present invention relates to a method and an apparatus for adjusting load applied by a suspension to a flying-type head slider.
2. Description of the Related Art
A flying-type thin-film magnetic head used for a magnetic disk drive and so on is generally made up of a slider and a magnetic head element provided at the trailing edge of the slider. The slider generally comprises a rail whose surface functions as a medium facing surface (an air bearing surface) and a tapered section or a step near the end on the air inflow side. When a recording medium is rotating, an airflow comes in from the tapered section or the step and passes between the recording medium and the slider. A lift is thus created and exerted on the slider. The slider flies above the surface of the recording medium by means of the lift.
The slider is flexibly supported by a suspension as a supporting device. The suspension generally incorporates: a plate-spring-shaped load beam made of stainless steel, for example; a flexure to which the slider is joined, the flexure being provided at an end of the load beam and giving an appropriate degree of freedom to the slider; and an attachment provided on the other end of the load beam and attached to an actuator that moves the slider across the track of the recording medium.
The suspension applies a load to the slider in the direction toward the surface of a recording medium while the slider is flying. Where a balance is maintained between the load applied by the suspension and the lift generated by the airflow passing between the recording medium and the rail of the slider, a narrow interval is kept between the medium facing surface of the slider and the recording medium while the slider is flying above the surface of the recording medium. The interval between the medium facing surface of the slider and the surface of the recording medium provided while the slider is flying is hereinafter called a flying height of a slider. The flying height of a slider has a great influence on performance of a magnetic head.
With a recent trend of magnetic heads toward smaller size and higher density, there have been intensifying demands for reduction and stability in the flying height of a slider. It is now difficult, however, to meet such demands merely by improving the shapes of the suspension and the medium facing surface of a slider, or merely by forming them with precision.
The flying height of a slider varies depending on the load applied to the slider by the suspension while the slider is flying. Therefore, to ensure stability and accuracy of the flying height of a slider as designed, it is significant that the load applied to the slider by the suspension while the slider is flying falls within a specified range. The load applied to the slider by the suspension while the slider is flying, which is sometimes called a gram load, is hereinafter referred to as a load under flying. It is difficult to make a direct measurement of a load under flying. Therefore, in practice, a suspension is deformed to attain the same state as that where the slider is flying at a specific flying height. Then, in this state, the load applied by the suspension to the slider is measured and the load thus measured is regarded as the load under flying. Such a load applied in this way to the slider under conditions equivalent to those where the slider is flying is hereinafter also referred to as a load under flying.
Where a suspension has just been manufactured, a load under flying supplied by the suspension may not always fall within a specified range. In response to this, several methods have been proposed for adjusting a load under flying supplied by a suspension. Three typical methods are described below.
A first method is to mechanically apply a force to the suspension to bend it, thereby adjusting the load.
A second method is to apply heat to the load beam of the suspension while applying an external force to the suspension, as disclosed in, for example, Published Unexamined Japanese Patent Applications (KOKAI) Heisei 5-159501 (1993), Heisei 5-189906 (1993) and Heisei 10-269538 (1998). In the method, heat is applied to the load beam while generating a stress in the load beam, thereby relieving the stress and thus reducing the load under flying supplied by the suspension. In this method, irradiation with laser light is generally employed as a method for applying heat to the load beam.
A third method, as disclosed in Published Unexamined Japanese Patent Application (KOKAI) Heisei 9-288874 (1997), for example, uses load adjusting fillets (strip-shaped portions) provided in a spring region of the load beam of the suspension. In this method, the load under flying is reduced by relieving stress in the spring region by irradiating the region with laser light, or by cutting one or a plurality of the fillets by irradiating the fillet(s) with laser light. On the other hand, the load is increased by contracting one or a plurality of the fillets by irradiating the fillet(s) with laser light.
However, it is difficult to achieve precise load adjustment with the first method. Furthermore, the first method may cause a curvature of the suspension that is different from what has been designed, which may adversely affect the properties of the suspension.
The second method has a problem in that the load cannot be increased for adjustment. Furthermore, since the second method applies heat to the load beam while applying an external force to the suspension, it involves complicated devices and steps for adjusting the load.
The third method also has a problem in that it makes a structure of the suspension complicated because of the fillets to be provided therein.
It is an object of the invention to provide a method and apparatus for adjusting a load applied to a flying-type head slider by a suspension, capable of both increasing and decreasing the load easily.
A method of the invention is provided for adjusting a load applied to a flying-type head slider by a suspension that supports the slider, the load being applied under conditions equivalent to those where the slider is flying. The method includes the steps of: holding the suspension while no external force to bend the suspension is applied to the suspension; and applying heat energy to the suspension to increase or decrease the load.
In the method of the invention, the load is adjusted by applying heat energy to the suspension while no external force to bend the suspension is applied to the suspension.
In the method of the invention, the suspension may be irradiated with laser light in the step of applying heat energy. In this case, gas for preventing oxidization of the suspension resulting from the irradiation with laser light may be sprayed on a spot on the suspension to be irradiated with the laser light.
In the method of the invention, the suspension may include a load beam for generating the load, the load beam being shaped like a plate spring and having two surfaces that face toward opposite directions, and, one of the two surfaces of the load beam may be selectively irradiated with the laser light in the step of applying heat energy.
The method may further include, before the step of applying heat energy, a step of measuring a parameter indicating an attitude of the suspension which is correlated with the load. Further, in the step of applying heat energy, conditions under which heat energy is applied to the suspension may be controlled based on the measured parameter.
The method of the invention may further include a step of measuring the load and determining whether the load is within a specified range, before and after the step of applying heat energy.
An apparatus of the invention is provided for adjusting a load applied to a flying-type head slider by a suspension that supports the slider, the load being applied under conditions equivalent to those where the slider is flying. The apparatus comprises: a holder (holding means) for holding the suspension while no external force to bend the suspension is applied to the suspension; and a heat energy applying device (means) for applying heat energy to the suspension to increase or decrease the load.
According to the apparatus of the invention, the load is adjusted by applying heat energy to the suspension while no external force to bend the suspension is applied to the suspension.
In the apparatus of the invention, the heat energy applying device (means) may have a laser light irradiating device for irradiating the suspension with laser light. In this case, the apparatus may further comprise a gas injecting device (means) for spraying gas for preventing oxidization of the suspension resulting from the irradiation with laser light on a spot on the suspension to be irradiated with the laser light.
In the apparatus of the invention, the suspension may include a load beam for generating the load, the load beam being shaped like a plate spring and having two surfaces that face toward opposite directions, and the laser light irradiating device may irradiate one of the two surfaces of the load beam selectively with the laser light.
The apparatus of the invention may further comprise: a position measuring instrument (attitude measuring means) for measuring a parameter indicating an attitude of the suspension which is correlated with the load; and a controlling device (means) for controlling conditions under which heat energy is applied to the suspension, based on the parameter measured by the position measuring instrument (attitude measuring means).
The apparatus of the invention may further comprise a load measuring instrument (means) for measuring the load.
Other and further objects, features and advantages of the invention will appear more fully from the following description.